It was a normal bounty-hunting day for reddit member u/hafooni, until hafooni realized that they have found themselves in Mexico. As you might know, there is no Mexico stage in the game itself. There was, back in the predecessor.
The thread post has gone viral since then, as it has spiked a lot of interest about this stage of the game. Is it a hidden location, is it an unfinished map, is it something that Rockstar wants to keep hidden, is it a message? Woah, the questions are endless, with so little answers.
However, the truth might not be as exciting as many would like it to be. What it appears to be at the moment is, a normal unfinished location, currently under development in Red Dead Online.
This is pure speculation, but it does appear that way.
There isn’t much official information being shared on the topic, but it seems like we might see Mexico appear in Read Dead Online soon enough.
Rockstar has been working nonstop on new content for Red Dead Online, as the player base only appears to grow in the last year or so. This might be the case for the Mexico map, that might come in a bigger update in the future.
